code: def test_unary_plus() -> None:
      data = [1, 2]
      df = pl.DataFrame({"x": data})
      assert df.select(+pl.col("x"))[:, 0].to_list() == data
  
      with pytest.raises(pl.exceptions.ComputeError):
          pl.select(+pl.lit(""))
  
file_path: polars/py-polars/tests/unit/operations/test_arithmetic.py
imports: from datetime import date, datetime, timedelta
  import numpy
  import pytest
  import polars
  from polars.testing import assert_series_equal
label_desc: Use image node_id 7 for calling a global function with example usage: test_unary_plus() without return types